Method and apparatus for measuring twist



Nov. 13, 1962 G. H. HUTCHENS ETAL 3,063,293

' METHOD AND APPARATUS FOR MEASURING TWIST Filed May 1, 1959 2Sheets-Sheet 1 Nov. 13, 1962 G. H. HUTCHENS ETAL 3,063,293

METHOD AND APPARATUS FOR MEASURING TWIST Filed May 1, 1959 2Sheets-Sheet 2 AMPLIFIER AND F CONTROL M56 cmcunnv United States Patent3,0633% METHOD AND APPARATUS FOR MEASURENG TWIST George H. Hutchens andWilliam L. Duncan, Wayneshero, Va, assignors to E. l. du Pont de Nemoursand Company, Wilmington, Del, a corporation of Delaware Filed May 1,195%, Ser. No. 810,436 9 Claims. (Cl. 73-160) This invention relates tothe production of strands from textile fibers and, more particularly, tothe measurement of twist in a continuously advancing strand.

In most textile and industrial applications, natural and/ or syntheticfibers are usually employed in the form of'a twisted strand, with thedegree and type of twist depending on the ultimate use of the strand.The term strand, as used herein, is intended to include either aregularly twisted or a false twisted monofilament, a filament yarn or astaple yarn, as well as the multi-ply yarns, threads, ropes or cordsproduced therefrom. The twist may be about the longitudinal axis of amonofilament strand or may follow a helical path as in a multiplystrand. The direction of twist is the same along the entire length of aregularly twisted strand and oscillates either in a random fashion or ina carefully controlled manner in a false twisted strand.

Known devices for measuring the amount of twist in a continuouslyadvancing strand are useful only in monitoring highly twisted cordscontaining at least two twisted plies or, if suitable for measuring thetwist in a single ply, do not function accurately on false twistedstrands or on yarns having a fuzzy surface. Furthermore, such knowndevices generally require extremely critical mechanical orientation ofthe strand being measured and equally critical adjustments andsynchronization of the device according to the type of strand beingmeasured. In these devices, the means for indicating the degree of twistis not such as to permit other than a direct visual observation.

The most important object of the present invention is to provide amethod and apparatus for measuring the twist in a continuously advancingstrand.

Another important object is the provision of a method and apparatus formeasuring twist in either a regularly twisted or a false twisted strand.

A further object is to provide an apparatus for measuring both theextent and direction of twist in an advancing strand without alteringany of its physical properties which apparatus includes means forindicating the degree of twist instrumentally.

With these and other objects in view, the monitoring apparatus of thepresent invention comprises generally a frame on which is situated amember having a smooth surface over which the advancing strand passes.As the strand passes over the surface, it tends to follow the twisttherein and to traverse the surface in the direction of twist. Theapparatus further includes a means responsive to the traversing tendencyof the strand for detecting both the extent and direction of twist. Themethod of the invention involves the steps of orienting a length of anadvancing strand, passing the oriented length over a smooth surface, andmeasuring traverse of the strand away from a linear path of travel overthe surface as 3,053,2h3i Patented Nov. 13., 1962 an indication of theextent and direction of twist in the strand.

The method and apparatus will be described more fully hereinafter, withreference to the accompanying drawings, wherein:

FIGURE 1 is a side view of a preferred embodiment of the monitoringapparatus of the present invention; and

FIG. 2 is an exploded view showing the details of the twist indicatingmechanism of FIG. 1.

In the apparatus embodiment chosen for illustration, a frame 10 providessupport for a package 12 from which a strand 14 is led through a pigtailguide 16 to a tension device 18. Strand 14 travels from tension device13 through a first reference guide 20, around a cylindrical rod 22, backthrough a second reference guide 24 and around a guide wheel 26. Rod 22is the terminal end of a member 23 which is mounted on frame 10. In aconstant speed feed system, which also functions to maintain uniformtension on the strand 14, the latter makes several passes around aspacing idler 3d and a feed pully 32 which is driven by a motor 34. Thestrand passes from the feed system through a guide 28 to a point ofultimate use. Although the strand source illustrated herein is thepackage 12, it is apparent that the monitoring apparatus of the presentinvention could as well be fed directly in a continuous process.

After leaving rod 22, the strand passes in close proximity to a follower38 which forms part of a means for detecting and indicating traversingmotion of the strand across rod 22. As shown more fully in FIG. 2, thedetecting and indicating means includes an elongated detection element40 which is pivoted on a jeweled bearing 42 in a casing 53. Element 4t?and follower 38 thus comprise a low friction, low inertia pointer havingthe spaced portions of follower 33 in bridging relationship to the lowerreach of strand 14. Also mounted on the element 44 is a shutter 44 whichregisters with and eclipses a portion of an aperture 4a in plate 48 whenstrand 14 is traveling the shortest path between aligned guides 20 and24. Movement of the shutter 44 in either direction varies the amount oflight passing from lamp 50 through aperture 46 to a measuringphotoelectric cell 52 which is coupled by wires 54 to amplifier andcontrol circuitry 56 from which a signal corresponding to the positionof shutter 44 may be passed to a suitable recording, control or visualindication instrument. This signal is proportional to the extent oftraverse and also indicative of the traverse direction.

In operation, the advancing strand will assume a posi tion on rod 22which is the resultant of the forces acting thereon. In passing betweentension device 18 and feed pully 32, there is a linear force exerted onthe strand which tends to position it along the shortest path of travelbetween the aligned reference guides 20 and 24. In passing around rod22, a lateral force is exerted by the tendency of the strand to followthe twist therein which of aperture 46 which is opened for the passageof light to cell 52 wherein a signal is generated and passed, throughcircuitry 56, to a potentiometer or other suitable means for recordingits amplitude either permanently or temporarily. When the yarn is in thezero twist position, the photo-electric detection system is in abalanced condition, i.e., the shutter 44 is in a position leavingapproximately half the aperture 46 open. The resulting output of cell 52is balanced out by adjusting the shutter 51 to provide an equal amountof light to compensating photo-cell 52', which is coupled by wires 54 tothe control circuitry 56. Accordingly, a positive or negative outputfrom the combined photo-cell system corresponds to movement of the yarnfrom the zero twist position.

In a continuous process, the signal from cell 52 could be used toregulate automatically the yarn-twisting mechanism to thereby minimizefluctuations in twist. The nature of the surface of cylindrical rod 22has an important effect on the operational efliciency of the process.Among the suitable materials which will provide low coefficient offriction between the surface of rod 22 and the advancing strand aresatin finish steel, chrome plated steel, glass and Al Si Mag, analuminum magnesium silicate ceramic. Although a straight cylindrical rodsubstantially normal to the line of advance of the strand has beenillustrated, other intercept angles may be used and the use of curvedbars is also practicable. The amount of tension in the advancing strandshould be maintained at a minimum consistent with satisfactoryoperation. With false twisted strands, high tension not only reduces thetraverse distance but may also pull out the false twist before it can bemeasured.

The method of the present invention involves the steps of advancing astrand continuously along its axis, orienting a length of the advancingstrand, passing that length over a smooth surface, and measuring thedeparture or traverse of the strand away from its shortest possible pathof travel over the surface. The advancing step may follow the spinningand twisting steps in a continuous process or may be accomplishedseparately, as shown in FIG. 1. The only requirement for the orientingor stabilizing step is that the strand advance linearly between twopoints, i.e., that a length be isolated. The passing step may beaccomplished as described in connection with the apparatus or in anumber of other ways. For example, an operator could exert a slighttension by causing the strand to pass over his finger. Similarly, themeasuring step may be accomplished in a number of ways, whether it beinstrumentally as described in connection with the apparatus; by using asuitable electronic or photo-electric cell position detection system; byrestraining lateral movement of the strand and measuring the restrainingforce with a suitable strain gage; by visual observation of a scalemounted proximal to rod 22; or with a ruler as the strand traverses aparticular smooth surface.

In an actual test of the instant method and apparatus, a continuousfilament cellulose acetate yarn (150 denier, 40 filaments) was falsetwisted for successive lengths at 1, 1.6, 2.7 and 3.3 maximum turns perinch and tested at a tension of 1 gram and a speed of 100 yards perminute, using an Al Si Mag rod /8 inch in diameter. Yarn traverse on therod was converted to an equivalent electrical signal by the detectingand indicating mechanism shown in FIG. 2. The signal was delivered to amillivolt recording potentiometer, with the results indicating aresolution of $0.2 turn per inch or an accuracy of 5%. In another test,continuous filament nylon yarn (150 denier, 40 filaments) was twistedfor successive lengths at zero twist, 1 turn per inch 8 twist, and 0.75turn per inch 2 twist and tested at a tension of 1 gram and a speed of100 yards per minute, using an Al Si Mag rod /2 inch in diameter. Thesample recordings indicated an obtained precision of better than 0.1turn per inch. In both instances, the yarn appeared unchanged aftertesting and a second testing yielded the same results, indicating thatthe testing method does not adversely affect product quality.

Other advantages inherent in the practice of this invention will occurreadily to those skilled in the art and, accordingly, its extent isintended to be limited only by the scope of the appended claims.

We claim:

1. An apparatus for measuring twist in a continuously advancingtensioned strand, said apparatus comprising: a support frame; a pair ofaligned, vertically spaced strand guides on said frame; a member on saidframe and spaced from said guides, said member having a smoothcylindrical surface around which the strand passes between the guides;an elongated element having a strand-following device thereon; and meanspivotally mounting the element on the frame for swinging movement of thedevice with the strand as the latter tends to follow the twist thereinand to thereby traverse said surface.

2. The apparatus of claim 1 wherein is provided an indicator mechanismcoupled with said element for indicating the extent and direction of thetraversing motion.

3. The apparatus of claim 2 wherein said indicator mechanism includes alight source, a photoelectric cell, an apertured plate between thesource and cell, and a shutter connected to said element, said shutterbeing positioned between the plate and said source.

4. An apparatus for monitoring the twist in a continuously advancingtensioned yarn-end, said apparatus comprising: a support frame; a pairof aligned, spaced yarn guides on said frame; an elongated cylindricalrod projecting out from the frame in spaced relationship to the guidesand with its axis substantially normal to the axis of the advancingyarn-end, said rod having a smooth surface over which the yarn-endpasses between the guides; and means coupled with the yarn-end fordetecting and indicating lateral movement of the yarn-end responsive tothe twist therein.

5. A method of measuring the twist in a continuously advancing tensionedstrand comprising the steps of: orienting a length of the advancingstrand; passing the oriented length over an elongated member providedwith a smooth surface, in intersecting relationship with and at anappreciable angle with respect to the axis of the member; and measuringtraverse of the strand on said surface away from its normal path oftravel as an indication of the extent and direction of twist in thestrand.

6. A method of checking the twist in a continuously advancing tensionedyarn-end comprising the steps of: orienting a length of the advancingyarn-end; diverting the path of said yarn-end in said length by passingit around a smooth cylindrical surface; and measuring the extent anddirection of yarn traverse on said surface as the yarn tends to followthe twist therein in passing over the surface.

7. An apparatus for measuring twist in a continuously and axiallyadvancing tensioned strand, said apparatus comprising: a support; anelongated member on the support, said member having a smooth surfaceover which the strand passes at an appreciable angle with respect to theaxis of the member; means on the support for detecting lateral movementof the strand as it tends to follow the twist therein in passing oversaid surface; and indicator means coupled with the detecting means forindicating the direction and extent of the movement.

8. An apparatus for measuring twist in a continuously advancingtensioned strand, said apparatus comprising: a support; an elongatedmember on the support, said member being provided with a smooth surfaceover which the strand passes axially and at an appreciable angle withthe axis of the member; means on the support for detecting twist in thestrand, said means including an element positioned adjacent the strandfor engagement therewith as the advancing strand tends to follow thetwist therein and thereby tends to traverse said surface; and indicatormeans coupled with said element for indicating the extent and directionof the strands tendencies to -folthe surface; and indicator meanscoupled with the detectlow the twist therein and traverse said surface.ing means for indicating the extent and direction of its 9. An apparatusfor measuring twist in a continuously movement.

advancing tensioned strand, said apparatus comprising: a

support frame; a pair of spaced-apart strand guides on the 5 ReferencesCited in the file Of this Patent frame; an elongated member on the framehaving 21 UNITED STATES PATENTS smooth surface over which the strandpasses axially and at an appreciable angle with the axis of the memberin its 2759324 Dean 1956 travel between the guides; means coupled withthe strand FOREIGN PATENTS for detecting lateral movement of theadvancing strand 10 107,779 Sweden June 29, 1943 as it tends to followthe twist therein in its travel over

